This application is directed to patch codes for color calibration job identification encoding. Typically, there are two phases involved in the color correction of a color printer: calibration and characterization. Calibration involves maintaining the printer at a defined state, while characterization involves determination of the multidimensional transformation or profile that relates device color signals (e.g. CMYK) to spectrophotometric or colorimetric signals (e.g. CIELAB). Typically, characterization is performed relatively infrequently, sometimes only once at the factory that produces the printer. Calibration, on the other hand, needs to be performed frequently to compensate for printer drift and bring the device back to its nominal state. While the term calibration will be used throughout this application, the ideas also apply equally to the characterization process.
The calibration process involves sending an image with pre-specified device signals (i.e. a target) to the printer, and making spectrophotometric measurements of the print with the use of a spectrophotometric scanner. The device and spectrophotometric signals together are used to build or update the calibration tables.
In a production environment, many printers, perhaps 30 to 40, might be going through a calibration process at the same time. In a typical environment, operators must manually keep track of each printed page, and there can be many printed target types printed for each printer. The operator must then feed each page to a spectrophotometric scanner and tabulate results of scanning each target type. The results of each scan must be manually associated to the corresponding printed target, and to the correct printer. Considering the quantity of pages printed and the amount of work necessary to manually track each printed page, there is considerable possibility for error. Pages can be accidentally misordered, and scanning results can accidentally be associated with an incorrect printed target or printer. This can result in highly inaccurate calibrations, and calls upon the difficult task of diagnosing the errors.
It would be desirable, therefore, to provide automation to the color printer calibration process, breaking the cycle where an operator must keep track of all details. It is further desirable that the job identification data be encoded according to a scheme wherein job identification data is printed according to a protocol and in a format approximately identical to a format of said target.